The unemployment rate for any group is defined as the number of unemployed people expressed as a percentage of the labour force (employed plus unemployed). As a measure of the proportion of the labour force that is under-utilised, its most important use is as an indicator of the performance of the economy. A high rate of unemployment indicates limited employment opportunities in a labour market that is oversupplied. A low rate of unemployment indicates a tight labour market, potential scarcity of skilled labour, and future cost pressures from wage demands from workers.

The trend over time in the overall unemployment rate serves as an indicator of the performance of the economy, while the unemployment rate for different groups of people (e.g. younger people, older people, women) identifies areas of social concern when rates for some groups are much higher than for others.